Smokable products, such as cigarettes and tobacco, contain carcinogenic compounds including polycyclic aromatic hydrocarbons (PAHs). Finding approaches to reduce the levels of these carcinogenic compounds has long been a goal in this technical art.
One approach to removing undesired components from cigarettes and tobacco smoke is the use of catalysts. Palladium catalyst systems have been proposed for cigarettes. Examples of background art in this technical area include the following U.S. patents: U.S. Pat. No. 4,257,430 to Collins et al.; U.S. Pat. No. 4,248,251 to Bryant et al.; U.S. Pat. No. 4,235,251 to Bryant et al.; U.S. Pat. No. 4,216,784 to Norman et al.; U.S. Pat. No. 4,177,822 to Bryant et al.; and U.S. Pat. No. 4,055,191 to Norman et al., each of which is incorporated by reference in its entirety. These early attempts at incorporating catalytic systems into mass-produced cigarettes have met with limited success. Therefore, there is a need in the art for a catalytic system that reduces the levels of certain carcinogenic or otherwise undesirable components from tobacco smoke, and which is amenable to use in mass-produced cigarettes, is desirable.
A more recent example of background art in this technical area is U.S. Pat. No. 6,789,548 to Bereman et al., which relates to a method for making a composition for smokable materials in general and in particular to catalytic systems that reduce the content of certain harmful or carcinogenic substances. Specifically, Bereman et al. discloses palladate salts, especially ammonium salts such as ammonium tetrachloropalladate and ammonium hexachloropalladate. In fact, many other background art approaches in this art area use hexachloropalladate forms which typically require high levels of Chloride and high pH solutions. Typically, these higher pH solutions are needed in order to achieve high solubility for the palladium. However, such high pH hexachloropalladate solutions can have dramatic negative effects on equipment and/or required additional steps be added to the process.
Further, Bereman et al. discloses that, on preferred embodiments, a catalyst system including catalytic metallic and/or carbonaceous particles and a nitrate or nitrite source is incorporated into the smokable materials so as to reduce the concentration of certain undesirable components in the resulting smoke (e.g., PAHs). Other background art approaches also require the use of nitrate to achieve their required reductions in PAHs.
Furthermore, Bereman discloses in embodiments wherein the particles are metallic; the particles are preferably prepared by heating an aqueous solution of a metal ion source and a reducing agent. Other previous patents have required the heating be between 50 and 90 degrees C. in order to aid in converting most of the soluble palladium to insoluble palladium. The additional requirements of adding nitrate/nitrite and heating, as discussed above, are examples of steps that are added to the process for treating smokable materials in the background art.
Therefore, there is a need in the art for an apparatus and method for application of palladium salts to smokable materials without the detrimental effects of high pH and additional preparation or processing steps often required with background art concentrations of hexachloropalladate. In addition, there is a need in the art for a method where no nitrate materials are required in order to achieve the necessary PAH reductions. Further, there is a need in the art for a palladium salt solution that can be applied without any additional heat requirements in order to convert soluble palladium into insoluble palladium. Furthermore, there is a need in the art for a Pd Salt solution that does not need to be mixed with other solvents or casings to achieve the desired affects. That is, so the normal tobacco casings and flavors can be processed separately and so that no catalytic effects are created due to these components.